Axial-piston machines, such as axial-piston pumps and axial-piston motors comprise a housing having a valve of fluid-distribution plate provided with a pair of kidney shaped ports communicating with an intake fitting and a discharge fitting for the hydraulic medium.
A cylinder drum rotates relative to this plate and is formed with an array of cylinders extending parallel to the axis of rotation of the drum, and successively brought into communication with the ports so that each cylinder bore alternately communicates with one port and the other. Within these cylinder bores there are provided individual pistons whose rods, projecting parallel to the axis of rotation, engage the drive flange or disk of the machine.
This drive disk is disposed in a plane which is inclined to the axis of rotation of the drum and hence to each of the piston rods or stems which are coupled therewith.
A shaft is rigidly fixed to this drive shaft and, in the case of an axial-piston motor, is connected to a load. In the case of an axial-piston pump, this shaft is connected to a driving source such as an electric motor or an internal combustion engine.
When hydraulic fluid is forced into the intake port, therefore, the pistons in the cylinders communicating therewith are driven outwardly and the driving force is transformed into a rotation of the drum and the drive flange to operate a load. Conversely, when the shaft is rotated, the pistons are entrained with the flange and, because of its inclination, are caused to undergo an inward and outward excursion which displaces fluid into an appropriate kidney-shaped port and draws fluid from the other so that the machine operates as a pump.
The term axial-piston machine, therefore, is used to designate both an axial-piston pump and an axial-piston motor.
In conventional systems, the drive flange is carried by the shaft and is supported in at least to axially spaced radially effective roller and ball bearing, and not engaged by an axially effective or thrust bearing. In another construction of the means for journaling this shaft, the latter is engaged by a single radial bearing and is engaged by a radially and axially effective (RADIAX) bearing spaced from the radial bearing.
The resultant of the forces applied by the pistons to the drive flange is thus resolved by the drive flange and shaft into an axial force component and a radial force component which are taken up by these bearings. However, because of the locations of these bearings, remote from the plane of the drive flange, considerably bending moment is applied to the drive flange.
The drive flange thus sustains a moment about a perpendicular to the shaft axis and to take up this moment a second radial bearing is generally required and is frequently provided. The greater the distance between the two radial bearings, the smaller the moment which can be taken up by them. Since large forces develop in axial-piston machines and the bearings thereof are highly loaded, the practice has been heretofore to space the radial bearings apart by relatively large distances, thereby making the apparatus larger than is desirable, increasing the amount of space which is required within the housing to accommodate the drive flange and its bearing system, and reducing the output of the machine per unit volume. A particular disadvantage is the large length of the machine to accommodate widely spaced bearing elements.